ZDNet’s Ed Bott has an amazing post up about the available storage on Microsoft’s new Surface Pro with Windows 8. There are a few more gigabytes than originally reported — Microsoft initially released a figure based on a not-final version of the device — and Ed did the math to determine that the 128GB Surface Pro has 89.7GB of space once you’ve accounted for Windows 8 and the recovery partition.

But he doesn’t stop there: He also discusses how much space Apple’s MacBook Airs offer (the same ballpark as the Surface Pros). And he explains that comparing Windows storage and Mac storage is an enormous pain, because Microsoft and Apple use different definitions of “gigabyte.”

Ed says that if you accuse Microsoft of gobbling up too much space with its operating system you should be equally nonplussed with Apple, since the situation with the MacBook Air is similar. It’s a reasonable point, and a reminder to product reviewers (such as me) that it would be a good idea to quote available-space figures for all the products we review which use sold-state storage. (Conventional hard drives are capacious enough that there’s no reason to stress out over the percentage occupied by the OS.)

I do respectfully disagree with Ed’s take, expressed near the end of his story, that even folks with lots of data to store should find a 128GB Surface Pro or MacBook Air “more than adequate.” I have a 256GB MacBook Air, and even that is on the tight side now that I’ve filled it with apps, photos, movies, music and a ginormous collection of PDFs and other digital reading material. But I still love the extreme, borderline obsessive-compulsive level of detail in his story. The Internet was made for stuff like this.